This invention relates to improvements to a flexible hose for interconnecting a portable tank with another tank to transmit fluids between the tanks. More particularly, this invention relates to a safety kit for automatically shutting off flow from the upstream tank to the downstream tank upon breakage of the flexible hose and/or breakage of the cable within the hose.
Various techniques have been used for transferring hazardous materials between a portable roadway vehicle tank and a fixed storage tank. Since the release of hazardous materials could result in a life-threatening situation, special precautions are taken to ensure that little if any hazardous material is released to the atmosphere during transfer of the material along the flexible hose assembly that connects the tanks. The flexible hose may be only a portion of the fluid transmission system between the tanks, but is an important link in the transfer of fluids to or from a portable tank, such as mounted on a roadway vehicle.
One prior art system marketed by Smart-Hose Technologies, Inc. utilizes a cable in compression which normally unseats valve members located at each end of the cable. In the event of hose separation, the valve members are released to stop the flow of product in both directions. The cable acts as a spring to maintain the valves off their seats, and the separation of the hose is intended to release the biasing force of the valves which then move to the closed position. A compressed cable extends between the hose ends and is installed during manufacture so that the user must purchase the assembly which includes the hose. In addition, it is difficult to verify the operational integrity of the system, since there is limited ability to check whether one of the valves has been frozen in the open position. During handling and coiling of the hose, special care must be taken not to bend the hose and compress the cable over a sharp radius or the cable will lose its ability to hold the valves open. If there is a failure of the hose, the entire system must be replaced, not merely the separated hose. Variations of the smart hose system are disclosed in U.S. Pat. Nos. 5,357,998 and 6,260,569, as well as publications 2001/00/35210 and 2002/00/7847.
Various other systems have been devised which are intended to close shutoff valves along the length of a flexible hose based upon a drop in monitored pressure when the hose breaks. Pressure monitoring systems for automatically closing the ends of a flexible hose have various reliability concerns. Near the completion of the unloading operation when the liquid level gets low in the tank, the sucking action at the pump inlet creates a vortex or whirlpool effect in the liquid, causing vapor to enter the pump in a random fashion. The entry of shots of vapor causes pump cavitation-like pressure spikes and drops which will shut-in a device that is triggered by the outlet pressure dropping below a given level. The device could be manually overridden when the tank is near empty to prevent the premature trip of the shutoff device. A separate problem, however, involves determining when the tank is near empty since the unloading time is a function of pressure and pump condition, and typically lasts for over 30 minutes. Even if one could determine when to engage and override, this will create a situation where the operator could override the device at will and defeat the purpose of a system which automatically closes off the ends of the hose. Moreover, even after the tank is empty, the pump is typically run for several minutes to push most of the liquid in the hose into the receiving vessel. This is done not only since the customer typically has paid for the product, but because venting of the liquid from the hose causes problems with nearby commercial or residential facilities due to the smell of vapor in the area of the tanks. Running a pump in this situation will thus always actuate a device that is triggered by low pressure and manual override options do not practically solve the problem.
The disadvantages of the prior art are overcome by the present invention. An improved flexible hose is hereinafter disclosed for transmitting hazardous fluids, such as propane and hydrodrous ammonia. More importantly, the present invention discloses a safety kit which automatically cuts off flow in the flexible hose in response to a hose separation or a break in the cable. The kit may be installed by the customer for use with an existing hose.
The present invention uses a flexible hose system for transmitting fluids from a portable tank to a stationary tank or from a stationary tank to a portable tank, or between two portable tanks. The hose assembly of the present invention need not be installed as part of the trailer equipment, and rather the flexible hose inclusive of the safety kit may be merely carried by the trailer operator and used during offloading or onloading independent of the equipment on the trailer. Also, the flexible hose system may be certified one time by a certified governmental agency engineer, and the system need not be inspected by a certified governmental inspector at installation time.
It is an object of the present invention to provide a safety kit for use with a flexible hose to interconnect a portable tank and another tank. The safety kit includes a control housing adapted for securing to one end of the hose, i.e., the upstream end, with the control housing containing a valve member moveable relative to a seating surface for opening and closing flow through the control housing. In a preferred embodiment, a cable is positioned in tension within the flexible hose and retains a trigger in a neutral position to keep the valve member open, such that fluids may be transmitted between the portable tank and the another tank. The trigger is also moveable to a hose break position in response to tensile force of the cable on the trigger for allowing the valve to move to the closed position. The cable support housing is adapted for securing to an opposing end of a flexible hose opposite the control housing, and secures the cable in a fixed axial position. Fluid pressure is thus transmitted through the hose when the trigger is in the neutral position, and a break in the hose results in movement of the trigger by the cable to the hose break position, thereby allowing the valve member to automatically close.
It is a feature of the invention that the trigger also includes a cable break position for closing the valve member with the cable breaks. The trigger is preferably biased to the cable break position.
A significant feature of the invention is that the safety kit includes a cable length compensator for preventing actuation of the trigger to the cable break position in response to a change in the position of the hose. In a preferred embodiment, the cable length compensator is an incompressible outer sheath which encloses the cable and extends between the cable support housing and the control housing. In alternate embodiments, the cable length compensator may include a long-throw trigger or a drum for winding a portion of the cable about the drum when the flexible hose is bent.
It is a further feature of the invention that a backcheck valve may be provided in the opposing end of the flexible hose for automatically closing to shut off flow in response to a break in the flexible hose.
It is a further feature of the invention that the safety kit may include either a piston-type valve or a flapper-type valve.
It is an object of the invention to provide an improved method to automatically close off flow through a flexible hose when interconnecting a portable tank with another tank. The method involves positioning a trigger with respect to the control housing, with the trigger being moveable from a neutral position for retaining the valve member open to a hose break position for allowing the valve member to move to the closed position. The end of the cable is secured to the cable support housing and the trigger such that the valve member, which may be biased closed, is held open by the cable when the trigger is in the neutral position. According to the method of the invention, the cable may be installed on a flexible hose in the field, and the cable cut to a selected length after measuring the length of the hose. Also, the position of the cable with respect to the cable support housing is adjustable, so that the user may test the hose for safety by bending the flexible hose and observing movement of the valve member and thereafter adjusting the position of the cable in response to the observed movement of the valve member.
In another embodiment, the safety kit retains the cable in compression to retain the valve member in the open position so that fluids may be transmitted between the portable tank and the another tank. The cable support housing includes a cable loading mechanism for placing the cable into compression to hold the valve member open.
It is a feature of this latter embodiment that the cable loading mechanism includes a screw jack base fixed with respect to the cable support housing and a screw jack threadably moveable on the screwjack base. In another embodiment, the cable loading mechanism may include a ratchet mechanism including a ratchet arm connected to the cable and a ratchet lever for advancing the ratchet arm to place the cable in compression within the flexible hose.
It is a significant advantage of the present invention that the safety kit may be purchased by the user of this hose and may be installed by the user without specialized equipment.
Yet another advantage of the invention is that the safety kit has a relatively low cost compared to prior art safety hoses which includes a cable in compression and a valve at both ends of the safety hose.
Another advantage of the invention is that the safety kit does not include components which must be installed on the portable vehicle or the stationary tank. All of the components of the kit are mounted on or within the flexible hose. Since the safety kit may be used with a conventional flexible hose, the utility of the hose with the flexible kit is significantly enhanced.
These and further objections, features, and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.